Insulator



UNITED STATES PATENT OEEICE.

'NATHAN T. FITCH, OF CHICAGO, lLlilNOlS.

lNSULATOR.

EPECEFICATION forming part of Letters Patent No. 349,788, dated September 2S, 1886.

Application tiled March (i, 158i.

To aZZ when?, it may concern..-

Be it known that I, Narnia' T. FiTon, a citizen of the United States, residing at Chicago, in the county of Cook and State of Illinois, have invented certain new and useful Improvcmentsin Insulators; and I hereby declare the following to be a full, clear, and eX- act description of the same.

My invention relates to the class of insulators which are used to support telegraph, telephone, and electric-light wires, and aresecu red for that purpose by means of metallic screws upon suitable supports.

It has hitherto been the-practice to provide the insulator with an opening extending longitudinally through its center, and of dimensions adapted to receive the shank of a screw, in which the screw-head forms a stop to prevent passage of the screw through the opening, the screw-threaded portion projecting bcyond the insulator to afford a ineans for securing it upon a support. rlhis construction makes the device undesirable, inasmuch as the screw-head, being exposed, provides a conducting medium for the electric current when the insulator is exposed to damp or wot weather, whereby iilni of moisture forms upon it and affords a conducting-surface for the eurreiit from the wire to the screw-head, whence it passes to the ground upon the moist surface ofthe insulatoi-suppoit and the post.

It is my object to prevent leading of the current, through the medium of the securing device, from its course upon the wire; and to this end my invention consists in an insulator provided with a screw or analogous securing device, the said securing device being embedded throughout a partol" its extent within the material forming the insulator, thus becoming incorporated with it and affording a strengthening medium, and projecting to the remainder olf its extent beyond the insulator.

In the drawings, Figure l is a perspective view of an insulator provided with my improvement. Figs. 2, 3, .l, and 5 are vertical sections of the same, showing modilieations.

A. is the body of the insulator, formed of insulating material, preferably of the compound Renewed July 2G, 19,56.

-iecting beyond it.

Serial No. 209,133. (No model.)

described and claimed in the J. I). Martin patent, No. 282,914, August 7, 1883.

l is a metallic screw, having its shank ernbedded within the insulator in the process of molding the saine, the threaded portion pro- The screw should be of a length sufficient to permit it to penetrate nearly to the top surface of the insulator, leaving a projecting portion sufficient to secure the device firmly upon its support. rllhe embedding of a considerable portion of the length of the screw within the material forming the insulator is desirable under all circumstances, since the largest frictionsurface is obtained, thus insuring rigidity of the screw in position; but it is particularly desirable, as the matcrial forming the insulators embodying my iinproveinent, like that hereinbefore specifically referred to, is frangible, since, being necessarily weakened. to a certain extent by the groove t, formed upon it,tlie screw, by extending above the groove, affords a strengthening medium, and prevents separation by fracture ofthe upper from the lower portion.

Various forms may be provided for the por tion of the screw contained within the insulator, that represented in Fig. 2 being of quadrangulai1 shape, in Fig. 3 a common headed screw. In Fig. l a screw having a T-slialred head is shown7 and Fig. 5 represents the screw as ilattened toward its upper end to increase the fri ction-surface. Other forms-for exam ple, that of an Lshaped head or of a lagscrew-present advantages equally desirable with those above described. rlhe object being to prevent the passage of the current vfrom the wire down the securing device, it is obvious that the same may also be effected with insulators provided with openings extending through them by filling the opening, after the insertion of the securing device, with pai'- a'ffine, sealing-wax, or other insulating substance. rlhis mode possesses disadvantages, however, and is therefore not the most desirable.

rlhe screw feature of the attaching niechan ism, though the preferred forni for use, is not absolutely essential, since other forms can be devised that will render the device praotioayextending therein above the groove to afford ble. Y a strengthening medium for the insulator, and ro What I claim as new, and desire to secure projecting to the remainder of its extent beby Letters Patent, isyoud the insulator, substantially as described.

5 The combination, with an insulator, A, of a screw, B, for securing the insulator upon its In presence of# t support', said screw being embedded through- THOMAS A. BANNING,

Y Yout a part of its extent within the insulator, DOUGLAS DYRENFORTH.

NATHAN T. FITCH. 

